Abstract
Alkaline-earth iron arsenide (122) is one of the most studied families of iron-based superconductors, especially for angle-resolved photoemission spectroscopy. While extensive photoemission results have been obtained, the surface complexity of 122 caused by its charge-non-neutral surface is rarely considered. Here, we show that the surface of 122 can be neutralized by potassium deposition. In potassium-coated BaFe2(As0.7P0.3)2, the surface-induced spectral broadening is strongly suppressed, and hence the coherent spectra that reflect the intrinsic bulk electronic state recover. This enables the measuring of superconducting gap with unpreceded precision. The result shows the existence of two pairing channels. While the gap anisotropy on the outer hole/electron pockets can be well fitted using an s± gap function, the gap anisotropy on the inner hole/electron shows a clear deviation. Our results provide quantitative constraints for refining theoretical models and also demonstrate an experimental method for revealing the intrinsic electronic properties of 122 in future studies.
Highlights
Alkaline-earth iron arsenide (122) is one of the most studied families of iron-based superconductors, especially for angle-resolved photoemission spectroscopy
While the alkaline-earth-metalterminated and arsenic-terminated surfaces have been observed by scanning tunneling microscopy (STM)[4,5,6,7], the alkaline-earthmetal-deficient surface exists with a reconstruction of alkaline-earth-metal atoms with 1 × 2 and √2 × √2 periods[6,7]
Angle-resolved photoemission spectroscopy (ARPES) is a powerful technique that measures the electronic structure of material in momentum space
Summary
Alkaline-earth iron arsenide (122) is one of the most studied families of iron-based superconductors, especially for angle-resolved photoemission spectroscopy. In potassium-coated BaFe2(As0.7P0.3)[2], the surfaceinduced spectral broadening is strongly suppressed, and the coherent spectra that reflect the intrinsic bulk electronic state recover This enables the measuring of superconducting gap with unpreceded precision. The 122 family is the most studied family of iron-based superconductors, due to its high sample quality, high superconducting transition temperature (Tc), tunable carrier density, and diversity of compounds with different chemical substitutions Aside from these advantages, the lattice structure of 122 contains a single alkaline-earth-metal plane and has no charge-neutral cleavage surface (Fig. 1a, b). The potassium deposition can be used as a practical experiment method for revealing the intrinsic electron structure and gap anisotropy of 122 iron-based superconductors in the future studies
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